The LTER (Long-Term Ecological Research) observatory HAUSGARTEN, in the eastern Fram Strait, provides us the unique ability to study the composition of benthic megafaunal communities through the analysis of seafloor photographs. This, in combination with extensive annual sampling campaigns, which have yielded a unique data set on faunal, bacterial, biogeochemical and geological properties, as well as on hydrography and sedimentation patterns, allows us to address the question of why variations in megafaunal community structure and species distribution exist within regional (60-110 km) and local (<4 km) scales.
Here, we present first results from the latitudinal HAUSGARTEN transect, consisting of three different stations (N3, HG-IV, S3) between 78°30’N and 79°45’N (2500m depth), obtained via the analysis of images acquired by a towed camera (Ocean Floor Observation System) in 2011. We assess variability in megafaunal densities, species composition and diversity as well as biotic and abiotic factors, which may cause the patterns observed. While there were significant differences in megafaunal composition and densities between all stations (N3 = 26.74 ±0.63; HG-IV = 11.21 ±0.25; S3 = 18.34 ±0.39 individuals/m2), significant local differences were only found at HG-IV.
We discuss our results in the context of sea ice coverage in the area and biogeochemical sediment parameters indicating food availability on the deep seafloor. These parameters were measured in parallel to the photographic transects, to develop the understanding of external factors that affect species distribution patterns amongst arctic benthic megafauna.
Finally, we focus on specific individual species, such as the sea cucumber Kolga hyalina and the amphipod Neohela lamia, that display particularly significant and varied distribution patterns across the latitudinal transect, as well as within each transect, in 2011 and other years. The results will be discussed in the context of diminishing sea ice coverage with projections of completely ice free areas within 30 years.